Process of making an aqueous viscoelastic automatic dishwash detergent containing a silicate-neutralized crosslinked polyacrylate

Abstract

An aqueous solution of an alkali metal neutralized polyacrylic acid and an alkali metal detergent builder salt and/or an alkali metal silicate is used as a base stock polymeric solution for the fomulation of an automatic dishwasher detergent composition which is a linear viscoelastic, pseudoplastic, gel-like aqueous product of exceptionally good physical stability, low bottle residue, low cup leakage, and improved cleaning performance. Linear viscoelasticity and pseudoplastic behavior is attributed by incorporation of cross-linked high molecular weight polyacrylic acid type thickener. Potassium to sodium weight ratios of at least 1/1 minimize amount of undissolved solid particles to further contribute to stability and pourability. Control of incorporated air bubbles functions to provide the product with a bulk density of about 1.35 to 1.40 g/cc which roughly corresponds to the density of the liquid phase. Stearic acid or other fatty acid or salt further improved physical stability.

What is claimed is: 
     
       1. A process for preparing a viscoelastic gel composition having a density of about 1.28 to about 1.42 grams/liter which comprises the steps of: (a) forming a predispersion (I) of water and a fatty acid or an alkali salt of a fatty acid, said fatty acid having about 8 to about 24 carbon atoms and at least one ingredient selected from the group consisting of a surfactant and a defoamer;   (b) forming an unneutralized premix solution (II) of a hydrated crosslinked polyacrylic acid in water, said hydrated crosslinked polyacrylic acid being crosslinked with 0.01 to 1.5 percent of a polyunsaturated monomer and said hydrated crosslinked polyacrylic acid having a molecular weight of about 500,000 to 10,000,000, the concentration of said hydrated crosslinked polyacrylic acid in said premix solution being about 2 to 8 wt. percent, said premix solution being used in sufficient quantity to provide 0.1 to 2 wt. percent, of said hydrated crosslinked polyacrylic acid in said composition;   (c) neutralizing the hydrated crosslinked polyacrylic acid with a 40 to 70 weight percent aqueous solution of an alkali metal silicate of form a gel solution (III) containing a neutralized polyacrylic acid thickening agent, said gel solution having a Brookfield viscosity at room temperature at 50 rpms at a #6 spindle of about 1,000 to 20,000 cps and having a pH of at least 10.0, said aqueous solution of said alkali metal silicate being used in sufficient quantity to provide 5.0 to 20.0 wt. percent of said alkali metal silicate in said composition;   (d) adding water (IV) to a mixing vessel;   (e) adding said gel solution (III) to said water (IV) in said mixing vessel;   (f) adding said predispersion (I) of step (a) to said gel solution (III) and water (IV) of step (e) in said mixing vessel;   (g) adding an alkali metal hydroxide to said water (IV) said predispersion (I) of step (a) and said gel solution (III) in said mixing vessel;   (h) adding potassium tripolyphosphate and/or potassium pyrophosphate to said water (IV), said predispersion (I) of step (a), said gel solution (III) and said alkali metal hydroxide in said mixing vessel;   (i) adding sodium tripolyphosphate to said water (IV), said predispersion (I) of step (a), said gel solution (III), said alkali metal hydroxide and said potassium pyrophosphate and/or said potassium tripolyphosphate in said mixing vessel to form said gel mixture;   (j) heating said gel of step (i) to a temperature of about 140° F. to about 200° F.;   (k) adding an alkali metal hypochlorite to the heated gel mixture of step (j) to form said gel composition; and   (l) cooling said gel composition of step (k) to a temperature of about 70° F. to about 90° F. and dearating said gel composition to less than about 1.5 volume percent of air, wherein the gel composition comprises approximately by weight:   ______________________________________                                    
Surfactant             0.00-5.0%                                          
Defoamer               0.00-1.5%                                          
Fatty acid and/or alkali                                                  
                       0.02-2.0%                                          
metal salt of fatty acid                                                  
Sodium tripolyphosphate                                                   
                       5.00-35.0%                                         
Potassium tripolyphosphate                                                
                       5.00-35.0%                                         
and/or potassium                                                          
pyrophosphate                                                             
Alkali metal hydroxide 0.50-8.0%                                          
Alkali metal silicate  5.00-20.0%                                         
Alkali metal hypochlorite                                                 
                       0.20-4.0%                                          
(% available chlorine)                                                    
Crosslinked polyacrylic acid                                              
                       0.10-2.0%                                          
Water                  Balance                                            
______________________________________                                    
       
     
     
       2. The process of claim 1 further including the step of adding a colorant to the water (IV) in the mixing vessel prior to the addition of said gel solution (III) in step (e) of claim 1. 
     
     
       3. The process of claim 1, further including adding a perfume to the gel composition subsequent to step (k) of claim 1.